StTCTP Positively Regulates StSN2 to Enhance Drought Stress Tolerance in Potato by Scavenging Reactive Oxygen Species

Drought is a negative agronomic effect that can lead to an increase in reactive oxygen species (ROS) levels. Excessive drought can severely alter cell membrane fluidity and permeability, significantly reducing cell viability. The <i>Gibberellic acid-stimulated Arabidopsis</i> (Snakin/GASA) gene family has an important role as antioxidants in inhibiting the accumulation of ROS and improving crop drought resistance. However, the regulatory mechanism of potato <i>StSnakin-2</i> (StSN2) in response to drought, along with how <i>StSN2</i> expression is regulated, is not well understood. In this study, we found that <i>StSN2</i> was induced by drought. Overexpression of <i>StSN2</i> significantly increased drought tolerance, whereas silencing <i>StSN2</i> increased sensitivity to drought. Overexpression of <i>StSN2</i> resulted in higher antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activity, and lowered hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) accumulation during drought stress. Also, overexpression of <i>StSN2</i> increased the relative water content (RWC) of leaves and reduced the water loss in leaves. We screened the upstream regulatory protein translation-controlled tumor protein (StTCTP) of <i>StSN2</i> through DNA pull-down combined with mass spectrometry. Yeast one-hybrid (YIH), electrophoretic mobility shift assay (EMSA), and luciferase reporting assay (LUC) indicated that StTCTP binds the <i>StSN2</i> promoter. Like <i>StSN2</i>, <i>StTCTP</i> was highly expressed in response to drought. Overexpression of <i>StTCTP</i> increased the photosynthetic rate and CAT enzyme activity, and lowered H₂O₂ and MDA accumulation during drought. Meanwhile, overexpression of <i>StTCTP</i> increased leaf RWC and reduced water loss. Our research strongly suggested that <i>StSN2</i> effectively cleared ROS and significantly boosted the drought resistance of potatoes. Furthermore, as a transcriptional activator of <i>StSN2</i>, <i>StTCTP</i>, much like <i>StSN2</i>, also enhanced the potato's drought tolerance. The results provided a foundation for the further study of <i>StSN2</i> regulatory mechanisms under drought stress.